Process for applying resinous coating to metal surface

ABSTRACT

Method and composition for applying a coating to a metal surface, the surface being contacted with an acidic aqueous coating composition comprising an organic coating-forming material, an acid, and a metal from a compound containing said metal, wherein the thickness and weight of the coating formed on the surface can be controlled by varying the amount of metal present in the composition and by varying the time the surface is contacted with the composition.

This is a continuation of application Ser. No. 446,032 filed Feb. 26,1974, now abandoned.

A conventional composition comprising a resin dispersed in water whichis utilized to form an organic coating on metal surfaces by immersingthe surfaces in the composition, will result in a coating whosethickness is the same regardless of the time the composition iscontacted with the surface. In order to obtain a thicker coating, it hasbeen necessary to subject the metal surface to a multiple stage coatingoperation or to employ a bath having higher solids content therein. Inaddition, these conventional systems ordinarily do not form organiccoatings on the metal surface which will initially resist rinsing,without a drying or fusing operation performed thereon.

U.S. Pat. No. 3,585,084 discloses compositions for coating metalsurfaces comprising an organic coating-forming material, an oxygencontaining oxidizing agent, hydrogen ion and an anion. Compositionscomprising a resin dispersion, hydrogen ion, fluoride ion, and anoxidizing agent selected from the group consisting of hydrogen peroxideand dichromate, for coating metal surfaces are disclosed in U.S. Pat.No. 3,592,699. The coating weight of coatings produced employingcompositions of this kind is a function of the time the surface iscontacted with the composition. These coatings are capable of beingrinsed prior to baking without removing all of the polymer or resindeposited on the surface.

Attempts have been made to adjust the rate at which these compositionsform a coating on metal surfaces, by varying the concentration ofhydrogen ion or oxidizing agent therein. It has been found that varyingthe concentrations and ratio of the constituents in these coatingcompositions in order to control the film-forming rate can affect theuniformity and appearance of the coating as well as the stability of theworking coating bath.

A serious problem that has been encountered in the use of coatingcompositions described in the aforementioned references is that as thecomposition is used to coat quantities of metal surfaces, thecomposition becomes unstable. This instability is characterized byflocculation, coagulation or jelling of the organic coating-formingmaterials in the composition. After these compositions become unstable,they can no longer be used effectively to coat metal surfaces and arethereby rendered inoperative.

Apparently, these compositions are rendered unstable by the build-up oflarge amounts of metal ions which are dissolved from the metallicsurface and are then oxidized by the oxidizing agent in the composition.As metal surfaces are continuously processed in these compositions, theamounts of these metal ions tend to build up to an undesirable level,thereby resulting in coagulation, flocculation or jelling of thedispersed resin therein. Attempts have been made to prevent thecomposition from becoming unstable by either removing the excess metalions from the composition or by adding additional dispersing agent tothe composition.

When these known compositions are contacted with, for instance ferrousmetal surfaces, apparently iron is dissolved from the surface by thehydrogen ions present in the composition to form ferrous ions. Theoxidizing agent in the composition acts on these ferrous ions to formferric ions. Due to the action of the oxidizing agent which oxidizes thealready dissolved metal ions to a higher valence state, thereby causingthe metal surfaces to be constantly attacked by the hydrogen ionpresent, undesirably high concentrations of ferric ions are accumulated.In a commercial operation, where large quantities of metal areprocessed, these known coating compositions will require constantreplenishment of dispersing agent or removal of metallic ions since theacid and oxidizing agent therein causes such high amounts of the ferricion to enter the bath, due to the vigorous attack of the metal surfaceby these constituents.

A constant stability problem arises in these compositions, since thereis constant generation of ferric ion, due to the conversion of ferrousion, and apparent interaction between the ferric ion and the dispersingagent which maintains the resin particles in the dispersed state,thereby causing coagulation and jelling.

It is an object of the present invention to provide an improved processfor forming an organic resinous coating on a metal surface. It is alsoan object of this invention to provide a method and composition forapplying resinous coatings to metal surfaces, the coating rate at whichsaid coatings are deposited, controlled by the amount of appropriatemetal present in the coating composition.

It is an object of this invention to provide a process for continuouslydepositing an organic coating on quantities of metal surfaces withoutthe rapid generation of large amounts of metallic ions which affect thestability of the composition.

A concomitant object of the present invention is to provide organiccoatings on metal surfaces, whose coating weight is a function ofcontact time with the coating composition.

It has been discovered that a uniform smooth organic coating can beformed on a metal surface in a short time by the use of an aqueouscoating composition consisting of a metal compound, acid, and particlesof resin dispersed therein. The coating thickness, or the rate at whicha coating is formed, can be readily controlled by adjusting the amountof metal added to the aqueous coating composition in the form of a metalcompound.

It should be understood that "aqueous coating composition" means theaqueous acidic composition having dispersed resin, metal from a metalcontaining compound, acid, and suitable additive ingredients asdescribed herein, which is employed in the process of this invention.

It should be understood that "metal surfaces" means various metalsurfaces, such as aluminum, zinc, iron, nickel, tin and lead surfacesand any other surface of metals which are selected from a group ofmetals ranging from aluminum to copper in the order of the "ionizationtendency", and which are present in the forms of pure metal and itsalloys and also in the forms of plated metal surfaces. The term "ironsurfaces" or "ferrous metal surfaces" employed herein thus encompasses awide variety of steels, iron, and iron alloys, including alloys of ironwith chromium and/or nickel. The term "aluminum surfaces" employedherein encompasses a wide variety of aluminum and aluminum alloys,including heat resistant alloys, corrosion resistant alloys and highstrength aluminum alloys.

The term "zinc surfaces" employed herein encompasses a wide variety ofzinc, zinc alloys and zinc plated metals, including hot dip galvanizedsteel and electrogalvanized steel. The term "copper surfaces" employedherein encompasses a wide variety of copper and copper alloys, includingbrass, bronze and German silver. The term "lead surfaces" employedherein encompasses a wide variety of lead and lead alloys, includingsoldering metals. The term "tin surfaces" employed herein encompasses awide variety of tin, tin alloys, and tin plated metals, including tinplate. The term "nickel surfaces" employed herein encompasses a widevariety of nickel, nickel alloys and nickel plated metals, includingnickel plated steel.

Of course, it is understood that the process of the present invention iscarried out in a substantially electrostatic field-free environment, andthe use of electricity and equipment and control instruments required tooperate an electrocoat process is avoided.

The particles of resin dispersed in the composition, will ordinarily bein the form of latex of the resin. Latices, dispersions of insolubleresin particles in water, are readily available and those soldcommercially can be utilized herein. These commercially availablelatices will usually contain other ingredients such as emulsifiers andprotective colloids. Examples of commercially available latices whichcan be employed and which can be regarded as the preferred materials foruse in the aqueous coating compositions of this invention are:

Hycar LX 407 (manufactured by Japanese Geon Co., Ltd.) . . . styrenebutadiene copolymer

Goodrite 1800 X 72 (manufactured by Goodrich Chemical Corp.) . . .styrene butadiene copolymer

Durex 637 (manufactured by W. R. Grace) . . . styrene butadienecopolymer

Pliolite 491 (manufactured by Goodyear Rubber and Chemical Corp.) . . .styrene butadiene copolymer

Hycar LX 814 (manufactured by Japanese Geon Co., Ltd.) . . . acryliccopolymer

Boncoat 9404 (manufactured by Dainippon Ink & Chemicals, Inc.) . . .acrylic copolymer

Nipole 1571 (manufactured by Japanese Geon Co., Ltd.) . . .acrylonitrile butadiene copolymer

Synthemal 9404 (manufactured by Nihon Reichold Co. Ltd.) . . . acryliccopolymer

Polysol AP 300 (manufactured by Kobunshi Kagaku Kogyo Co., Ltd.) . . .acrylic copolymer

Polysol EVA P 1 (manufactured by Kobunshi Kagaku Kogyo Co., Ltd.) . . .ethylene-vinyl acetate copolymer

Poly-em 40 (manufactured by Gulf Oil Corp.) . . . polyethylene

Other coating-forming resin dispersions or emulsions can be employedherein so long as the latex is stable in the presence of the otheringredients in the compositions of the present invention.

The amount of dispersed resin employed in the coating composition willdepend on the amount of resin which can be dispersed therein and theamount needed to provide sufficient resinous material to form a coating.The concentration of dispersed resin can vary over a wide range andshould preferably be from about 5 to about 550 g/l of resin. It isunderstood that the volume of latex necessary to provide the particularamount of resin in the coating composition will depend on the specificamount of resin solids dispersed in the latex to be employed.

For the coating process of the present invention to be effected, theconcentration of metal in the coating composition should be maintainedby employing a water soluble metal compound or a metal compound solublein acidic aqueous compositions. The metal compound can be present in thecomposition in an amount from about 0.025 grams/liter to about 50grams/liter. The concentration of metal in the composition will dependon the particular metal and metal compound employed. For example, ferricfluoride can be added to the coating composition in an amount from about1.0 gram/liter to about 50 grams/liter and silver fluoride can be addedto the bath in an amount from about 0.1 grams/liter to about 10grams/liter. A wide variety of metal compounds can be employed in thepractice of the present invention. Selection of the compound to beemployed will depend on its commercial availability and its ability toliberate metal in the aqueous coating composition.

For example, metal compounds which will yield sufficient metal in theaqueous acidic coating composition for aluminum surfaces and zincsurfaces are ferric fluoride, ferrous oxide, ferric oxide, cupricsulfate and cobaltous nitrate. Metal compounds which will yieldsufficient metal in the aqueous acidic coating compositions for ferrous,tin, and lead surfaces are ferric fluoride, ferrous oxide, ferricphosphate and silver fluoride. Metal compounds which will yieldsufficient metal in the aqueous acidic coating composition for coppersurfaces are silver fluoride and silver acetate.

It is noted that subject matter disclosed herein and relating to the useof metal compounds which comprise ferric iron is disclosed and claimedin co-pending U.S. patent application Ser. No. 445,434, filed February25, 1974, now abandoned, in the names of Nishida, an applicant herein,and Hirohata, said application being a continuation of U.S. patentapplication Ser. No. 232,625, filed Mar. 7, 1972, now abandoned. Thesubject matter of Ser. No. 445,434 is incorporated in two copendingcontinuation-in-part applications, Ser. Nos. 797,758 and 797,759, bothfiled May 17, 1977. The omission of claims herein covering subjectmatter relating to the use of metal compounds comprising ferric iron isnot to be construed as an abandonment of such subject matter inasmuch assuch subject matter is disclosed and claimed in the aforementionedco-pending applications.

The acid to be employed in the composition of the present invention canbe an inorganic or an organic acid. Typical examples of inorganic acidsthat can be employed are sulfuric, hydrochloric, hydrofluoric, nitric,and phosphoric acid. Examples of organic acids that can be employed areacetic, chloracetic, and trichloracetic acid. The acid to be employed inthe process of the present invention must be present in sufficientquantity to maintain the pH of the solution at its desired level. The pHof the coating composition should be maintained at a level within therange of from about 1.6 to about 5.0.

The acid employed in the composition will dissociate to yield hydrogenion and an anion. It has been observed that particularly good resultsare obtained when the acid employed in the coating composition ishydrofluoric acid. The preferred method of making the composition acidiccomprises the use of hydrofluoric acid, which permits a simple means forcontrol of pH in the coating composition and introduces an anion, thatis fluoride ion, which allows for satisfactory operation of the process.The use of hydrofluoric acid prevents the deliberate inclusion of anionswhich may be undesirable and detrimental to the coating process. Itshould be understood that hydrofluoric acid is a preferred acid to beemployed in the aqueous coating composition, but that other acids suchas those described above can be employed with satisfactory results.

A preferred embodiment of this invention is to employ an operatingaqueous coating composition comprising a combination of constituentsconsisting essentially of an anionic stabilized resin dispersion(negatively charged dispersed resin particles) having about 5 to about550 grams/liter of resin solids, from about 1 to about 5 grams/liter offerric fluoride trihydrate, and an acid in an amount sufficient toimpart a pH to the aqueous composition of from about 1.6 to about 5.0.

A distinct advantage of the present process is that large quantities ofmetal surfaces can be contacted with the aqueous coating composition,for example, with little build-up of ferric ion caused by the acidattack on the ferrous metal surface. The present invention allows forcontrolled amounts of ferric ion in the coating composition. It has beenfound that the metal loss from a surface contacted with the aqueouscoating composition will not exceed 40 mg per square foot per minute.The process of the present invention can be continuously effected forlonger periods of time on greater quantities of metal.

In the coating operation, the metal substrate to be treated is broughtinto contact with the aqueous coating composition under suitableconditions of temperature and contact time. The time of treatment of themetal surface with the aqueous coating composition can be from about 15seconds to about 10 minutes. It will be appreciated that with the use ofthe aqueous coating composition described herein, the coating weight ofthe deposited coating will increase with longer exposure of the metalsurface to the action of the coating composition. Therefore, the coatingtime to be employed will depend on the coating weight desired.Preferably, contact time between metal substrate and coating compositionshould be from about 30 seconds to about 5 minutes. It should be notedthat the coating weight for a particular coating composition willincrease up to a maximum as the time of treatment is increased.

The coating process can be operated at temperatures from about 40° F. toabout 120° F. It is preferable to operate the coating bath at ambienttemperature, that is from about 60° F. to about 90° F. Generally, aslight change in the temperature of the aqueous coating composition willnot necessitate substantial alteration of treating time andconcentration parameters.

The process of the present invention can be effected by employing knowncontacting techniques. Contact can be effected by either immersion orflowcoating to produce the desired surface coating. Preferably, theaqueous coating composition will be contacted with the metal surface byconventional immersion methods.

Subsequent to contact with the aqueous coating composition, the surfaceshould be dried to allow the resin to be fused. Prior to the dryingoperation, the coated surface can be exposed to an oxidative environmentand then rinsed with water. It has been found that when the surface isexposed to an oxidative environment, such as allowing the surface tostand in air, for a time from about 15 seconds to about 10 minutes,followed by water rinsing, and then dried, the surface possesses atight, adherent, and uniform coating. It should be understood that thetime of exposure to air or other oxidative environment should not belong enough to allow the deposited coating to dry prior to rinsing. Theexposure time to be employed will depend somewhat on the type of resinutilized to form the coating.

Subsequent to the water rinse, the coated surface can be rinsed with anaqueous rinse solution containing hexavalent chromium or hexavalentchromium and reduced forms of chromium. Subsequent to the rinsetreatment, the coated surface should be dried or baked. This can beaccomplished by conventional techniques, such as passing the metalsurface through a heated environment such as an oven, subjecting it to awarm air stream, or by allowing it to dry at ambient temperature. Shouldspeed be a necessary factor, any method of forced drying the surface canbe accomplished. When a heated environment is used, drying may becarried out at temperatures above 150° F., and preferably from about300° F. to about 500° F. It should be understood that whatevertemperature is employed will depend to some extent on the type of latexor resin dispersion and the drying time that has been utilized.

The aqueous coating compositions of the present invention describedhereinabove are capable of producing coatings on a metal surface whichportray excellent adhesion to the surface and have excellent corrosionresistant properties. However, the aqueous coating compositions and thecoatings deposited can be enhanced by incorporation into the coatingcomposition of added constituents described hereinbelow.

An oxidizing agent may be incorporated into the aqueous coatingcomposition. Any oxidizing agent can be employed and can be convenientlyadded to the composition as a water soluble compound. Typical examplesof oxidizing agents that can be used are hydrogen peroxide, dichromate,permanganate, nitrate, persulfate, and perborate. In some instances, theaddition of an oxidizing agent to the composition in an amountsufficient to provide from about 0.01 to about 0.2 of oxidizingequivalent per liter of composition may be desirable to obtain a coatinghaving particular properties, such as heavier coating weights. It hasbeen observed that addition of an oxygen containing oxidizing agent tothe aqueous coating composition can result in higher coating weightsthan would ordinarily be obtained employing the same contact time.Should an oxygen containing oxidizing agent be employed in thecomposition, it will be appreciated that the working coating bath willrequire regorous control procedures, since the composition, when incontact with the metal workpieces, will generate large amounts or metalions. It will be appreciated that addition of an oxidizing agent to theaqueous coating composition is not deemed desirable when largequantities of metals are to be processed. (The term "oxidizingequivalent" when used herein means the number of grams of oxidizingagent used, divided by the equivalent weight of the oxidizing agent. Theequivalent weight of the oxidizing agent is the gram molecular weight ofthe agent divided by the changing valence of all stoms in the moleculewhich change valence, usually one element.)

A coalescing agent can be incorporated into the aqueous coatingcomposition. The addition of a coalescing agent will further enhance theappearance and the corrosion resistant qualities of the depositedcoating. A typical example of a coalescing agent which can be employedis ethylene glycol monobutyl ether. The coalescing agent can be presentin the composition in an amount from about 5 grams/liter to about 30grams/liter.

The coating composition of the present invention may be formulated so asto incorporate water dispersible pigments known to the art. Variationsin the color of the deposited coating can be realized by adding pigmentssuch as phthalocyanine blue, phthalocyanine green carbon black,quinacridone red, iron oxide red, iron oxide yellow, lead chromate, andchrome oxide green. These pigments provide excellent color variationswith no sacrifice in coating quality or corrosion resistance.

To assure satisfactory wetting of the metallic surface during treatmentwith the coating composition, it may be desirable to incorporate intothe composition a small amount of a wetting agent or surface activeagent. Preferably, nonionic or anionic type wetting agents should beemployed. Typical examples of wetting agents which can be utilized arealkyl phenoxy polyethoxy ethanol and sodium salts of alkylaryl polyethersulfonate.

Should a dry pigment be used in the coating composition, it can bedispersed in the aqueous coating composition by conventional procedures,such as mixing the pigment with a small amount of nonionic or anionicsurface active agent and water, said mixture agitated with a high speedmixer, then adding the pigment - surface active agent mixture to thealready prepared coating composition with further agitation.

A pigment, such as iron oxide red or iron oxide yellow, which ispartially soluble in the aqueous coating composition, can be employed asa source for metal, particularly iron. Should the pigment be employed toserve as a source for iron, a sufficient amount of pigment must be addedto provide sufficient iron in the composition to effect the process ofthe present invention.

To demonstrate the present invention, a series of examples are presentedshowing the use of particular aqueous coating compositions. It will beobserved that some of the examples include the use of various otheradditives which have been found to be suitable for use in thecompositions. The examples presented below are illustrative of thisinvention and are not considered as limiting for other materials andoperative conditions falling within the scope of the invention thatmight be substituted.

In some of the examples below, corrosion tests and adhesion tests wererun on the test panels. When salt spray corrosion tests were run onrepresentative panels, the treated panels were scribed so that basemetal was exposed. Panels were subjected to 5% salt spray and were ratedinaccordance with ASTMB-1654-61, by measuring the average failure of thepaint film from the scribe.

Adhesion tests were run on panels, using impact and cross-hatch testprocedures which are commonly employed in the testing of paints. In theimpact test, the test surface is impacted by a falling 1/2 inch ballwith a force measured as 50 kilogram centimeters, thereby deforming thetest surface. Subsequent to impact, the deformed surface is inspectedfor loose or cracked paint, usually on the reverse side of the impact,and rated in inches of paint failure. In the crosshatch test, thesurface is scribed with parallel lines, approximately 1 millimeter apartand out through to bare metal. Duplicate lines are scribed at rightangles to make a crosshatch pattern. Scotch brand cellophane tape ispressed smoothly over the scribed area. After several seconds, the tapeis pulled back rapidly so that the tape is turned back upon itselfapproximately 180° from its original pressed position. Results arereported in the degree of failure noted, that is none, slight, moderate,or heavy loss of coating.

EXAMPLE 1 - 7

Panels of each metal described in Table 1, cleaned in a conventionalalkali metal silicate cleaning solution, were immersed for 3 minutes inan aqueous coating composition comprising the following constituents:

    ______________________________________                                        Component                 Grams.                                              ______________________________________                                        Styrene-butadiene resin (HYCAR LX 407)                                                                  180                                                 Hydrofluoric acid         3                                                   Ferric fluoride (trihydrate)                                                                            5                                                   Water to make 1 liter                                                         ______________________________________                                    

Hycar LX 407 was employed as the source for the stryrenebutadiene resin,(manufactured by Japanese Geon Co., Ltd., and containing 48% resinsolids). The aqueous composition was prepared by mixing the resin withwater, and adding hydrofluoric acid, and ferric fluoride with continuousagitation.

The test panels were removed from the coating bath and dried in an ovenat 356° F. for 10 minutes. The average coating weight for the panelswere as shown in Table 1, and the coatings produced were observed to besmooth and uniform.

                  Table 1                                                         ______________________________________                                                               Coating Weight                                         EXAMPLE NO.                                                                              Metal Surface     mg/ft.sup.2                                                                           (g/m.sup.2)                              ______________________________________                                        1          dull steel.sup.*1 1673    (18)                                     2          aluminum.sup.*2   1951    (21)                                     3          high strength Al alloy.sup.*3                                                                   2138    (23)                                     4          zinc.sup.*4       1673    (18)                                     5          hot dip galvanized steel.sup.*5                                                                 1766    (19)                                     6          tin plate.sup.*6  1394    (15)                                     7          lead.sup.*7       1301    (14)                                     ______________________________________                                         .sup.*1. JIS G-3141, SPC-C                                                    .sup.*2. JIS H-4000, A-1050P                                                  .sup.*3. JIS H-4000, A-2024P                                                  .sup.*4. JIS H-4321, First Class                                              .sup.*5. JIS G-3302, SPG-2C                                                   .sup.*6. JIS G-3303, SPT-E                                                    .sup.*7. JIS H-4301, PbP                                                 

EXAMPLE 8 - 58

These Examples were run to illustrate the use of various metal compoundsas the source for metal ion in the aqueous coating composition.

The constituents in the respective compositions are reported below inTable 2, along with the measured average weight of the coatingsproduced.

The aqueous compositions employed in Examples 8 - 58 were prepared asset forth in Example 1 - 7, except that different sources for metal wereemployed in each case.

Panels of each metal described in Table 2 were cleaned in a conventionalalkali metal silicate cleaning solution, then immersed in the respectivecoating composition set forth in Table 2 for 3 minutes. The pH of eachaqueous coating composition employed herein was between 1.6 and 5.0. Thepanels were dried in an oven at 356° F. for 10 minutes.

The average weight of the coating on the test panels was measured and isnoted in Table 2.

                                      Table 2                                     __________________________________________________________________________                                            Metal panel                           Ex.                                                                              Latex Used and                                                                             Resin                                                                             Source for metal                                                                       HF         used as a                                                                             Coating weight                No.                                                                              Resin therein                                                                              (g/l)                                                                             (g/l)    (g/l)      Substrate                                                                             (g/mg)                                                                            mg/ft                     __________________________________________________________________________     8 HYCAR LX 407, styrene                                                                      180 Ferric oxide                                                                           3.5                                                                              Water to make                                                                         Dull Steel                                                                            (15)                                                                              1394                         butadiene        10          1 liter                                        9 "            180 Ferric oxide                                                                           3.5                                                                              "       aluminum                                                                              (19)                                                                              1766                                          10                                                        10 "            180 Ferric oxide                                                                           3.5                                                                              "       High strength                                             10                  aluminum alloy                                                                        (21)                                                                              1952                      11 "            180 Ferric oxide                                                                  10       3.5                                                                              "       Zinc    (14)                                                                              1301                      12 "                Ferric oxide        Hot dip                                               180 10       3.5                                                                              "       galvanized                                                                            (16)                                                                              1487                                                              steel                                 13 "            180 Ferric oxide                                                                  10       3.5                                                                              "       tin plate                                                                             (11)                                                                              1022                      14 "            180 Ferrous oxide                                                                 10       3.5                                                                              "       Dull Steel                                                                            (10)                                                                              929                       15 "            180 Ferrous oxide                                                                 10       3.5                                                                              "       Aluminum                                                                              (16)                                                                              1487                      16 "            180 Ferrous oxide                                                                 10       3.5                                                                              "       High strength                                                                         (17)                                                                              1580                                                              aluminum alloy                        17 "            180 Ferrous oxide                                                                 10       3.5                                                                              "       zinc    (12)                                                                              1115                      18 HYCAR LX 407, styrene                                                                      180 Ferrous oxide                                                                             Water to make                                                                         Hot dip (11)                                                                              1022                         butadiene        10       3.5                                                                              1 liter galvanized                                                                    steel                                 19 "            180 Ferrous oxide                                                                          3.5                                                                              "       Tin plate                                                                              (7)                                                                               651                                          10                                                                            Ferric phosphate                                          20 "            180 (tetrahydrate)                                                                         2.0                                                                              "       Mill scaled                                                                           (14)                                                                              1301                                          6                   steel                                                     Ferric phosphate                                          21 "            180 (tetrahydrate)                                                                         2.0                                                                              "       Aluminum                                                                              (19)                                                                              1766                                          6                                                                             Ferric phosphate                                          22 "            180 (tetrahydrate)                                                                         2.0                                                                              "       Zinc    (15)                                                                              1394                                          6                                                                             Ferric phosphate                                          23 "            180 (tetrahydrate                                                                          2.0                                                                              "       Tin plate                                                                             (12)                                                                              1115                                          6                                                                             Ferric phosphate                                          24 "            180 (tetrahydrate)                                                                         2.0                                                                              "       Lead    (11)                                                                              1022                                          6                                                                             Ferrous phosphate                                         25 "            180 (octahydrate)                                                                          2.0                                                                              "       Mill scaled                                                                            (7)                                                                               651                                          6                   steel                                                     Ferrous phosphate                                         26 "            180 (octahydrate)                                                                          2.0                                                                              "       Aluminum                                                                              (11)                                                                              1022                                          6                                                         27 HYCAR LX 407, styrene                                                                          Ferrous phosphate                                                                         Water to make                                    butadiene    180 (octahydrate)                                                                          2.0                                                                              1 liter Zinc     (9)                                                                               836                                          6                                                                             Basic ferric                                              28 "            180 acetate  3.0                                                                              "       Dull steel                                                                            (16)                                                                              1487                                          5                                                                             Basic ferric        High strength                         29 "            180 acetate  3.0                                                                              "       aluminum alloy                                                                        (17)                                                                              1580                                          5                                                                             Basic ferric        Hot dip                               30 "            180 acetate  3.0                                                                              "       galvanized                                                                            (15)                                                                              1394                                          5                   steel                                                     Basic ferric                                              31 "            180 acetate  3.0                                                                              "       Tin plate                                                                              (8)                                                                               744                                          5                                                                             Basic ferric                                              32 "            180 acetate  3.0                                                                              "       Lead     (7)                                                                               651                                          5                                                                             Chromium fluoride                                         33 "            180 (trihydrate)                                                                           1.5                                                                              "       Zinc    (10)                                                                               929                                          3                                                                             Cadmium fluoride    High strength                         34 "            180 4        2.5                                                                              "       aluminum alloy                                                                         (8)                                                                               744                                          Cobaltous nitrate                                         35 "            180 (hexahydrate)                                                                          3.5                                                                              "       Millscaled                                                                             (9)                                                                               836                                          10                  steel                                                     Cobaltous nitrate                                         36 HYCAR LX 407, styrene                                                                      180 (hexahydrate)                                                                          3.5                                                                              Water to make                                    butadiene        10          1 liter Aluminium                                                                              (7)                                                                               651                                          Cobaltous nitrate   Hot dip                               37 "            180 (hexahydrate)                                                                          3.5                                                                              "       galvanized                                                                            (12)                                                                              1115                                          10                  steel                                                     Stannous fluoride   High strength                         38 "            180 6        2.0                                                                              "       aluminum alloy                                                                        (15)                                                                              1394                                          Stannous Fluoride                                         39 "            180 6        2.0                                                                              "       Zinc    (17)                                                                              1580                                          Lead dioxide                                              40 "            180 8        3.5                                                                              "       dull steel                                                                            (16)                                                                              1487                                          Cupric sulfate                                            41 "            180 10       3.0                                                                              "       Aluminum                                                                               (9)                                                                               836                                          Cupric sulfate      Hot dip                               42 "            180 10       3.0                                                                              "       galvanized                                                                            (15)                                                                              1394                                                              steel                                                     Silver fluoride                                           43 "            180 5        2.0                                                                              "       Dull steel                                                                            (23)                                                                              2138                                          Silver fluoride     Mill scaled                           44 "            180 5        2.0                                                                              "       steel   (20)                                                                              1859                                          Silver fluoride                                           45 "            180 5        2.0                                                                              "       Aluminum                                                                              (20)                                                                              1859                         HYCAR LX 407, styrene                                                                          Silver fluoride                                                                           Water to make                                                                         High strength                         46 butadiene    180 5        2.0                                                                              1 liter aluminum alloy                                                                        (26)                                                                              2416                      47 "            180 Silver fluoride                                                                        2.0                                                                              "       Zinc    (16)                                                                              1487                                          5                                                         48 "            180 Silver fluoride                                                                        2.0                                                                              "       Hot dip (17)                                                                              1580                                          5                   galvanized                                                                    steel                                 49 "            180 Silver fluoride                                                                        2.0                                                                              "       Nickel plated                                                                         (20)                                                                              1859                      50 "            180 Silver fluoride                                                                        2.0                                                                              "       Lead    (11)                                                                              1022                                          5                                                         51 "            180 Silver fluoride                                                                        2.0                                                                              "       Copper  (17)                                                                              1580                                          5                                                         52 "            180 Silver fluoride                                                                        2.0                                                                              "       Brass   (15)                                                                              1394                                          5                                                         53 "            180 Silver acetate                                                                         2.5                                                                              "       Dull steel                                                                            (19)                                                                              1766                                          6                                                         54 "            180 Silver acetate                                                                         2.5                                                                              "       High strength                                                                         (17)                                                                              1580                                          6                   aluminum alloy                        55 "            180 Silver nitrate                                                                         2.5                                                                              "       Zinc    (16)                                                                              1487                                          6                                                         56 "            180 Silver nitrate                                                                         2.5                                                                              "       Nickel plated                                                                         (13)                                                                              1208                                          6                   steel                                 57 HYCAR LX 407, styrene                                                                      180 Silver nitrate                                                                         2.5                                                                              Water to make                                                                         Copper  (13)                                                                              1208                         butadiene        6           1 liter                                       58 "            180 silver nitrate                                                                         2.5                                                                              "       Brass   (14)                                                                              1301                      __________________________________________________________________________                        6                                                     

EXAMPLE 59 - 72

These Examples were run to illustrate the use of various acids as thesource for acid in the aqueous coating composition. The constituents inthe respective coating compositions are reported below in Table 3, alongwith the measured average weight of the coatings produced.

The aqueous coating composition employed in Example 59 - 72 wereprepared as set forth in Example 1 - 7, except that different sourcesfor acid were employed in each case.

Panels of each metal described in Table 3 were cleaned in a conventionalalkali metal silicate cleaning solution, then immersed in the respectivecoating composition set forth in Table 3 for 3 minutes. The pH of eachaqueous coating composition employed herein was between 1.6 and 5.0.

The panels were then dried in an oven at 356° F for 10 minutes. Theaverage weight of the coating on the test panels was measured and isnoted in Table 3.

                                      Table 3                                     __________________________________________________________________________                                               Metal panel                        Ex.                                                                              Latex Used and                                                                             Resin                                                                             Source for metal                                                                       Acid          used as a                                                                             Coating weight             No.                                                                              Resin therein                                                                              (g/l)                                                                             (g/l)    (g/l)         substrate                                                                              (g/m.sup.2)                                                                       mg/ft.sup.2           __________________________________________________________________________    59 HYCAR LX 407, styrene                                                                      200 Ferric fluoride                                                                        Phosphoric                                                                          Water to make                                                                         Dull steel                                                                            (20) 1859                     butadiene        10       acid  1 liter                                                                 6                                                60 "            "   "        "     "       Aluminum                                                                              (28) 2602                  61 "            "   "        "     "       High strength                                                                         (29) 2695                                                             aluminum alloy                     62 "            "   "        "     "       Zinc    (18) 1673                  63 "            "   "        "     "       Hot dip (19) 1766                                                             galvanized                                                                    steel                              64 "            "   "        "     "       Tin plate                                                                             (13) 1208                  65 "            "   "        "     "       Lead    (13) 1208                  66 "            "   "        Sulfuric                                                                            "       Mill scaled                                                                           (8)  744                                                acid          steel                                                           4                                                67 "            "   "        "     "       Aluminum                                                                              (8)  744                   68 "            "   Ferric fluoride                                                                        "     "       Hot dip (17) 1580                                      (trihydrate)           galvanized                                             10                     steel                              69 "            "   10       Acetic                                                                              "       Dull steel                                                                            (14) 1301                                               acid                                                                          10                                               70 HYCAR LX 407, styrene                                                                      200 Ferric fluoride                                                                        Acetic                                                                              Water to make                                                                         High strength                                                                         (17) 1580                     butadiene        (trihydrate)                                                                           acid  1 liter aluminum alloy                                         10       10                                               71 "            "   "        "     "       Zinc    (18) 1673                  72 "            "   "        "     "       Tin plate                                                                             (12) 1115                  __________________________________________________________________________

EXAMPLE 73 - 83

These Examples were run to illustrate the use of various resins as thesource for resin in the aqueous coating composition. The constituents inthe respective coating compositions are reported below in Table 4, alongwith the measured average weight of the coatings produced.

The aqueous coating compositions employed in Example 73 - 83 wereprepared as set forth in Example 1 - 7, except that different sourcesfor resin were employed in each case.

Panels of each metal described in Table 4 were cleaned in a conventionalalkali metal silicate solution, then immersed in the respective coatingcomposition set forth in Table 4 for 3 minutes. The pH of each aqueouscoating composition employed herein was between 1.6 and 5.0.

The panels were then dried in an oven at 356° F. for 10 minutes. Theaverage weight of the coating on the test panels was measured and isnoted in Table 4.

                                      Table 4                                     __________________________________________________________________________                                            Metal panel                           Ex.                                                                              Latex Used and                                                                             Resin                                                                             Source for metal                                                                       HF         used as a                                                                             Coating weight                No.                                                                              Resin therein                                                                              (g/l)                                                                             (g/l)    (g/l)      substrate                                                                             g/m.sup.2)                                                                        mg/ft.sup.2               __________________________________________________________________________    73 Boncoat 9404,    Ferric fluoride                                                                        2  Water to make                                                                         Dull steel                                                                            (13)                                                                              1208                         acrylic copolymer                                                                          220 (trihydrate)                                                                              1 liter                                                           6                                                         74 "            220 "        "  "       Aluminum                                                                              (16)                                                                              1487                      75 "            220 "        "  "       Zinc    (16)                                                                              1487                         Nipole 1571                                                                76 acrylonitrile                                                                              180 "        "  "       Mill scaled                                                                           (14)                                                                              1301                         butadiene copolymer                  steel                                 77 "            180 "        "  "       High strength                                                                         (34)                                                                              3160                                                              aluminum alloy                        78 "            180 "        "  "       Hot dip                                                                       galvanized                                                                            (22)                                                                              2045                                                              steel                                 79 "            180 "        "  "       Tin plate                                                                             (7) 651                       80 Primal ASE-60,                                                                             300 "        "  "       Dull steel                                                                            (13)                                                                              1208                         polyacrylic acid                                                           81 "            300 "        "  "       Aluminum                                                                              (16)                                                                              1487                                                              Hot dip                               82 "            300 "        "  "       galvanized                                                                    steel   (19)                                                                              1766                      83 "            300 "        "  "       Lead    (6) 558                       __________________________________________________________________________

EXAMPLE 84 - 89

Panels of each metal described in Table 5 were immersed in the aqueouscoating composition comprising the following constituents:

    ______________________________________                                        Component                 Grams                                               ______________________________________                                        Styrene-butadiene resin (HYCAR LX 407)                                                                  200.0                                               Hydrofluoric acid         2.5                                                 Hydrogenperoxide          1.5                                                 Ferric fluoride (trihydrate)                                                                            3.0                                                 water to make 1 liter                                                         ______________________________________                                    

The test panels were contacted with the coating composition for a periodof 3 minutes, then dried in an oven at 320° F. for 15 minutes. Theaverage weight of the coatings is also listed in Table 5. It has beenalso observed in further experiments that the average weight of thecoatings decreased by about 3 - 10 grams/m² when each metal paneldescribed in Table 5 were immersed in the aqueous coating compositioncomprising the above-mentioned constituents but hydrogenperoxide.

                  Table 5                                                         ______________________________________                                        Ex.        Metal panel used as a                                                                           Coating weight                                   No.        substrate         (g/m.sup.2)                                                                           mg/ft.sup.2                              ______________________________________                                        84         Dull steel        (31)    2881                                     85         Aluminum          (18)    1673                                     86         Zinc              (26)    2416                                     87         Tin plate         (15)    1394                                     88         Lead              (12)    1115                                     89         Copper            (13)    1208                                     ______________________________________                                    

EXAMPLE 90 - 94

Panels of each metal described in Table 6 were immersed in the aqueouscoating composition comprising the following constituents. The testpanels were contacted with the coating composition for a period of 2minutes, then dried in an oven at 392° F. for 5 minutes. The averageweight of the coatings produced is also listed in Table 6.

It should be noted that the aqueous coating composition employed hereincontained chromic acid as an oxygen containing oxidizing agent, andbutylcellosolve as a coalescing agent.

    ______________________________________                                        Component                 Grams                                               ______________________________________                                        Styrene butadiene resin (HYCAR LX 407)                                                                  160                                                 Hydrofluoric acid         3                                                   Chromic acid anhydride    1                                                   Ferric phosphate (tetrahydrate)                                                                         8                                                   Butylcellosolve           10                                                  Water to make 1 liter                                                         ______________________________________                                    

                  Table 6                                                         ______________________________________                                        EXAMPLE                      Coating weight                                   NO.        Metal Surface      (g/m.sup.2)                                                                          mg/ft.sup.2                              ______________________________________                                        90         Dull steel        (21)    1952                                     91         High strength Al alloy                                                                          (27)    2509                                     92         Hot dip galvanized steel                                                                        (23)    2138                                     93         Tin plate         (12)    1115                                     94         Brass             (15)    1394                                     ______________________________________                                    

EXAMPLE 95 - 101

Various metal panels noted in Table 7 were employed in this procedure.The test panels were cleaned in a conventional alkali metal silicatecleaning solution and then immersed in the aqueous coating compositiondescribed below. The panels were then baked in an oven at 392° F. for 5minutes. The average coating weight of the coatings produced wasmeasured and is listed in Table 7.

    ______________________________________                                        Component                 Grams                                               ______________________________________                                        Styrene butadiene resin (HYCAR LX 407)                                                                  180                                                 Lead chromate pigment     95                                                  Anionic surface active agent (Demol-P)                                                                  5                                                   Ferric fluoride (trihydrate)                                                                            8                                                   Hydrofluoric acid         3                                                   Water to make 1 liter                                                         ______________________________________                                    

It will be observed that lead chromate pigment was employed in thecomposition. The lead chromate, an anionic surfactant (Demol-P) andwater were mixed together and milled for 16 hours prior to addition tothe already prepared composition containing the styrene butadiene resin,hydrofluoric acid and water.

The lead chromate pigment employed in the composition was Kiku-Jirushi G(manufactured by Kikuchi Kogyo).

                  Table 7                                                         ______________________________________                                        Ex.        Metal panel used as a                                                                           Coating weight                                   No.        substrate         (g/m.sup.2)                                                                           mg/ft.sup.2                              ______________________________________                                        95         Dull steel        (120)   11152                                    96         aluminum          (45)    4182                                     97         High strength     (44)    4089                                                aluminum alloy                                                     98         Zinc              (66)    6134                                     99         Hot dip galvanized steel                                                                        (89)    8271                                     100        Tin plate         (1110)  10223                                    101        Lead              (32)    2974                                     ______________________________________                                    

EXAMPLE 102 - 107

Panels of each metal described in Table 8 was immersed in the aqueouscoating composition comprising the following constituents:

    ______________________________________                                        Component                 Grams                                               ______________________________________                                        Styrene-butadiene resin (HYCAR LX 407)                                                                  200                                                 Lead chromate pigment (KIKU-JIRUSHI 50-3KB,                                   manufactured by Kikuchi Kogyo)                                                                          50                                                  Ferric oxide pigment (MAPICO YELLOW LL.XLO,                                   manufactured by Titan Industry)                                                                         30                                                  Anionic surface active agent (EMAL 10,                                        manufactured by KaO-Atlas)                                                                              3                                                   Hydrofluoric acid         3.5                                                 Tap water to make 1 liter                                                     ______________________________________                                    

The test panels were contacted with the coating composition for a periodof 3 minutes, then dried in an oven at 356° F for 10 minutes. Theaverage coating weight for the panels were shown in Table 8, and thecoatings produced were observed to be smooth and uniform.

                  Table 8                                                         ______________________________________                                        Ex.                          Coating weight                                   No.        Metal surface     (g/m.sup.2)                                                                           mg/ft.sup.2                              ______________________________________                                        102        Dull steel        75      6970                                     103        Aluminum          57      5297                                     104        Zinc              72      6691                                     105        Nickel plated steel                                                                             10       929                                     106        Tin plate         76      7063                                     107        Lead              37      3439                                     ______________________________________                                    

EXAMPLE 108 - 130

Various metal panels were cleaned in a conventional alkali metalsilicate cleaning solution and then immersed in the aqueous coatingcomposition described in Table 9 for 3 minutes. The panels were thenbaked in an oven at 392° F for 5 minutes. The average coating weight ofthe coatings produced was measured and is listed in Table 9.

                                      Table 9                                     __________________________________________________________________________                             Surface Source for                                   Ex.                                                                              Latex used and                                                                         Resin                                                                             Pigment  active agent                                                                          metal   HF      Metal Coating weight         No.                                                                              resin therein                                                                          (g/l)                                                                             (g/l)    (g/l)   (g/l)   (g/l)   surface                                                                             (g/m.sup.2)                                                                       mg/ft.sup.2        __________________________________________________________________________    108                                                                              HYCAR LX 407,                                                                          200 Lead chromate,                                                                         Demol-P Ferric phos-                                                                          2  Water to                                                                           Dull steel                                                                          (98)                                                                              9108                  styrene butadiene                                                                          Kiku J.5G-3KB                                                                          4       phate      make 1                                                             tetrahydrate                                                 80               5          liter                             109                                                                              "        "   "        "       "       "  "    High  (48)                                                                              4461                                                                strength                                                                      aluminum                                                                      alloy                                                                         Hot dip                      110                                                                              "        "   "        "       "       "  "    galvanized                                                                          (69)                                                                              6412                                                                steel                        111                                                                              "        "   "        "       "       "  "    Tin plate                                                                           (73)                                                                              6784               112                                                                              "        "   "        "       "       "  "    Lead  (34)                                                                              3160               113                                                                              "        160 Iron oxide red,                                                               Todacolor KR-R                                                                         Demol-P Pigment used                                                                          3.5                                                                              "    Dull steel                                                                          (31)                                                                              2881                               60       5                                                    114                                                                              "        "   "        "       "       "  "    Aluminum                                                                            (22)                                                                              2045               115                                                                              "        "   "        "       "       "  "    Zinc  (30)                                                                              2788               116                                                                              "        "   "        "       "       "  "    Lead  (15)                                                                              1394                  Nipole 1571, Moraco Carbon                                                                          Emulgen 930,                                                                          Ferric fluoride                                                                          Water to                          117                                                                              acrylonitrile-                                                                         250 H, Columbia C.                                                                         Kao-Atlas,                                                                            trihydrate                                                                            2.5                                                                              make 1                                                                             Dull steel                                                                          (20)                                                                              1859                  butadiene    30       1       5          liter                                Nipole 1571, Moraco Carbon                                                                          Emulgen 930,                                                                          Ferric fluoride                                                                          Water to                          118                                                                              acrylonitrile.                                                                         250 H, Columbia C.                                                                         Kao-Atlas.                                                                            trihydrate                                                                            2.5                                                                              make 1                                                                             Aluminum                                                                            (26)                                                                              2416                  butadiene    30       1       5          liter                             119                                                                              "        "   "        "       "       "  "    Hot dip                                                                       galvanized                                                                          (27)                                                                              2509               120                                                                              "        "   "        "       "       "  "    Tin plate                                                                           (13)                                                                              1208                  HYCAR LX 407,                                                                          180 Cyanine Blue                                                                           Emal 10,                                                                              Silver fluoride                                                                          Water to                          121                                                                              styrene-butadiene                                                                          KR, Sanyo                                                                              Kao-Atlas,                                                                            6       3  make 1                                                                             Dull steel                                                                          (25)                                                                              2342                               Shikiso  0.5                liter                                             15                                                            122                                                                              "        "   "        "       "       "  "    Mill scaled                                                                   steel (19)                                                                              1766               123                                                                              "        "   "        "       "       "  "    Aluminum                                                                            (24)                                                                              2230                                                                High                         124                                                                              "        "   "        "       "       "       strength                                                                      aluminum                                                                            (27)                                                                              2509                                                                alloy                        125                                                                              "        "   "        "       "       "  "    Zinc  (21)                                                                              1952                                                                Hot dip,                     126                                                                              "        "   "        "       "       "  "    galvanized                                                                          (20)                                                                              1859                                                                steel                        127                                                                              "        "   "        "       "       "  "    Nickel                                                                        plated                                                                              (22)                                                                              2045                                                                steel                           HYCAR LX 407,                                                                              Cyanine Blue                                                                           Emal 10,                                                                              Silver fluoride                                                                          Water to                          128                                                                              styrene  180 KR, Sanyo                                                                              Kao-Atlas,                                                                            6       3  make 1                                                                             Lead  (12)                                                                              1115                  butadiene    Shikiso  0.5                liter                                             15                                                            129                                                                              "        "   "        "       "       "  "    Copper                                                                              (20)                                                                              1859               130                                                                              "        "   "        "       "       "  "    Bronze                                                                              (19)                                                                              1766               __________________________________________________________________________

EXAMPLE 131

Steel panels were employed in this procedure. The test panels werecleaned in a conventional alkali metal silicate cleaning solution andthen immersed in the aqueous coating composition described below fordifferent contact times. The test panels were then allowed to stand inair for 3 minutes and then rinsed with water. The panels were then bakedin an oven at 356° F. for 10 minutes. The average coating weight of thecoatings produced was measured and is listed in Table 10.

    ______________________________________                                        Component                 Grams                                               ______________________________________                                        Styrene butadiene resin (HYCAR LX 407)                                                                  180                                                 Lead chromate pigment     50                                                  Iron oxide red pigment    50                                                  Anionic surface active agent (Demol-P)                                                                  5                                                   Hydrofluoric acid         3.5                                                 Water to make 1 liter                                                         ______________________________________                                    

It will be observed that lead chromate pigment and iron oxide redpigment were employed in the composition. The lead chromate, iron oxidered, an anionic surfactant (Demol-P) and water were mixed together andmilled for 16 hours prior to addition to the already preparedcomposition containing the styrene butadiene resin, hydrofluoric acidand water. The pH of the aqueous coating composition was measured at2.8.

The lead chromate pigment employed in the composition was Kiku-Jirushi5G (manufactured by Kikuchi Kogyo) and iron oxide red pigment was TenyoBengara 501 (manufactured by Tone Sangyo).

                  Table 10                                                        ______________________________________                                                             Coating Weight                                           Time of Immersion    mg/ft.sup.2                                              ______________________________________                                        15 sec.               649                                                     30 sec.               803                                                      1 min.              1224                                                      2 min.              2257                                                      3 min.              3544                                                      5 min.              5608                                                     ______________________________________                                    

As can be seen from Table 10, the coatings deposited on test panelstreated in accordance with the present invention have the property ofincreased coating weight with increased contact time.

EXAMPLE 132

Steel panels were employed in this procedure. The test panels werecleaned in a conventional alkali metal silicate cleaning solution andthe immersed in the aqueous coating composition described below for 3minutes. The coated test panels were then exposed to the air for periodsof time as noted below and then were rinsed with water. The panels werethen baked in an oven at 356° F. for 10 minutes.

    ______________________________________                                        Component                 Grams                                               ______________________________________                                        Styrene butadiene resin (HYCAR LX 407)                                                                  180                                                 Lead chromate (Kiku Girushi 5G)                                                                         50                                                  Iron oxide (Tenyo Bengara 501)                                                                          50                                                  Anionic surface active agent (Demol-P)                                                                  5                                                   Hydrofluoric acid         3                                                   Water to make 1 liter                                                         ______________________________________                                    

It will be observed that lead chromate pigment and iron oxide redpigment were employed in the composition. The lead chromate, iron oxide,and anionic surfactant (Demol-P) and water were mixed together andmilled for 16 hours prior to addition to the already preparedcomposition containing the styrene butadiene resin, hydrofluoric acidand water. The coatings produced were observed to be smooth and uniform.The average film thickness was measured and is listed in Table 11. Thetest panels were subjected to 168 hours salt spray corrosion tests andthe results are listed in Table 11.

                  Table 11                                                        ______________________________________                                                 Film thickness                                                                             Scribe failure                                                   (microns)    (in inches)                                             ______________________________________                                         5 sec.    13             1/32                                                15 sec.    17             1/32                                                30 sec.    22             1/32                                                 1 min.    25             1/32                                                 2 min.    28             1/32                                                 3 min.    28             3/32                                                ______________________________________                                    

Impact tests, cross-hatch tests, and salt spray corrosion test were runon representative panels treated in accordance with some of theaforementioned procedures, that is, Example 1, 2, 4, 6 and 51. Theresults of these tests are listed in Table 12 and also in Table 13.

                                      Table 12                                    __________________________________________________________________________           Film Appearance                                                        Coating                                                                              + coating weight                                                                        Impact Test                                                                          Cross Hatch                                                                            Metal                                        Composition                                                                          in (gr/m.sup.2)                                                                     mg/ft.sup.2                                                                       Results                                                                              Test Results                                                                           Surface                                      __________________________________________________________________________    Ex. No.  1                                                                           Good (18)                                                                           1673                                                                              No failure                                                                           None     Dull steel                                   Ex. No.  2                                                                           Excellent No failure                                                                           None     Aluminum                                            (21)  1952                                                             Ex. No.  4                                                                           Good (18)                                                                           1673                                                                              No failure                                                                           None     Zinc                                         Ex. No.  6                                                                           Excellent No failure                                                                           None     Tin plate                                           (15)  1394                                                             Ex. No. 51                                                                           Good (17)                                                                           1580                                                                              No failure                                                                           None     Copper                                       __________________________________________________________________________

                                      Table 13                                    __________________________________________________________________________           Film Appearance                                                        Coating                                                                              + coating weight Salt spray                                                                             Metal                                        Composition                                                                          in    (gr/m.sup.2)                                                                      mg/ft.sup.2                                                                          test results*                                                                          surface                                      __________________________________________________________________________    Ex. No. 102                                                                          Excellent                                                                           (75)                                                                              6970   No failure                                                                             Dull steel                                   Ex. No. 103                                                                          Good  (57)                                                                              5291   No failure                                                                             Aluminum                                     Ex. No. 104                                                                          Excellent                                                                           (72)                                                                              6691   Slight white-rust                                                                      Zinc                                         Ex. No. 106                                                                          Excellent                                                                           (76)                                                                              7063   No failure                                                                             Tin plate                                    Ex. No. 129                                                                          Good  (20)                                                                              1859   No failure                                                                             Copper                                       __________________________________________________________________________     *Exposure time : 150 hours)                                              

As can be seen from Table 12 and 13, test panels treated in accordancewith the present invention give acceptable adhesion and corrosion testresults.

We claim:
 1. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition, the metal of said compound selected from the group consisting of silver, iron in its divalent state, copper in its divalent state, cobalt in its divalent state, chromium in its trivalent state, cadmium, tin in its divalent state and lead in its tetravalent state, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.
 2. A process according to claim 1 wherein said metal-containing compound is selected from the group consisting of silver fluoride, silver acetate, silver nitrate, ferrous oxide, ferrous phosphate, cupric sulfate, cobaltous nitrate, chromium fluoride, cadmium fluoride, stannous fluoride, and lead dioxide.
 3. A process according to claim 1 wherein said surface is immersed in said composition for a period of time within the range of about 15 seconds to about 10 minutes.
 4. A process according to claim 3 wherein said surface is immersed in said composition for a period of time within the range of about 30 seconds to about 5 minutes.
 5. A process according to claim 1 wherein said composition has a temperature within the range of about 40° F. to about 120° F.
 6. A process according to claim 5 wherein said composition has a temperature within the range of about 60° F to about 90° F.
 7. A process according to claim 1 including fusing the resin of said coated surface after it is withdrawn from said composition.
 8. A process according to claim 7 wherein said resin is fused by subjecting the coating surface to a temperature within the range of about 150° F. to about 500° F.
 9. A process according to claim 7 wherein prior to fusing said resin, the resinous coated surface is subjected to an oxidative environment.
 10. A process according to claim 9 wherein said resinous coated surface is exposed to an oxidative environment by exposing it to air for a period of time within the range of about 15 seconds to about 10 minutes.
 11. A process according to claim 9 wherein subsequent to being exposed to said oxidative environment, the resinous coated surface is rinsed with water and thereafter the resin is fused.
 12. A process according to claim 7 wherein the resinous coated surface is contacted with an aqueous solution of hexavalent chromium or hexavalent chromium and reduced forms of chromium prior to fusing said resin.
 13. A process according to claim 1 wherein said coating composition includes an oxidizing agent.
 14. A process according to claim 13 wherein said oxidizing agent is hydrogen peroxide in an amount of about 0.01 to about 0.2 oxidizing equivalent per liter of composition.
 15. A process according to claim 1 wherein said composition includes a coalescing agent.
 16. A process according to claim 15 wherein said coalescing agent is ethylene glycol monobutylether in an amount of about 5 to about 30 g/l.
 17. A process according to claim 1 wherein said coating composition comprises a pigment.
 18. A process according to claim 17 wherein said metal-containing compound and said pigment comprise iron oxide red or iron oxide yellow.
 19. A process according to claim 1 wherein said resin is anionically stabilized.
 20. A process according to claim 1 wherein said composition includes a pigment, wherein said composition has a temperature within the range of about 60° F. to about 90° F., wherein said surface is immersed in said composition for a period of time of about 30 seconds to about 5 minutes and wherein said resinous coated surface is exposed to air for a period of time of about 15 seconds to about 10 minutes after it is withdrawn from said composition, and including contacting the resinous coated surface with an aqueous solution of hexavalent chromium or hexavalent chromium and reduced forms of chromium, and thereafter fusing the resin of said resinous coated surface at an elevated temperature.
 21. A process according to claim 20 wherein said resin is anionically stabilized.
 22. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and including metal selected from the group consisting of chromium, cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition and contains said metal, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.
 23. A process according to claim 22 wherein said resin is anionically stabilized.
 24. A process according to claim 22 wherein said metal is silver, the source of which is about 0.1 to about 10 g/l of silver fluoride.
 25. A process according to claim 22 wherein the metal loss from said surface is not in excess of 40 mg/sq.ft./min.
 26. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from hydrofluoric acid, and about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition, the metal of said compound selected from the group consisting of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.
 27. A process according to claim 26 wherein said metal surface is selected from the group consisting of iron, aluminum, zinc, copper, lead, tin, and nickel surfaces.
 28. A process according to claim 26 wherein said metal surface is an iron surface.
 29. A process for applying a resinous coating to a metal surface comprising immersing the surface in an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles, and of pH within the range of about 1.6 to about 5 and prepared from about 0.025 to about 50 g/l of a metal-containing compound which is soluble in said composition, the metal of said compound selected from the group consisting of silver, iron in its divalent state, copper in its divalent state, cobalt in its divalent state, cadmium, tin in its divalent state and lead in its tetravalent state, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is immersed in said composition, and withdrawing the resinous coated surface from said composition.
 30. A process for applying a resinous coating to a metal surface comprising contacting the surface with an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles, and of pH within the range of about 1.6 to about 5 and including metal selected from the group consisting of cobalt, copper, silver, cadmium, tin, lead, and ferrous iron, the source of said metal being a metal-containing compound which is soluble in said composition and contains said metal, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition.
 31. A process for applying a resinous coating to a metal surface comprising contacting the surface with an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles anionically stabilized, and of pH within the range of about 1.6 to about 5 and prepared from a metal-containing compound which is soluble in said composition, the metal of said compound selected from the group consisting of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition.
 32. A process for applying a resinous coating to a metal surface comprising contacting the surface with an acidic aqueous coating composition comprising about 5 to about 550 g/l of solid resin particles, the resin being selected from the group consisting of styrene-butadiene, acrylic copolymers, acrylonitrile-butadiene, ethylene-vinyl acetate, polyethylene, and polyacrylic acid, and of pH within the range of about 1.6 to about 5 and prepared from a metal-containing compound which is soluble in said composition, the metal of said compound selected from the group consisting of non-ferric transition elements and Group IV elements of the Periodic Table, said composition being effective in forming on said metal surface a resinous coating which increases in weight or thickness the longer said surface is contacted with said composition. 